A narrow QRS does not predict a normal left ventricular function in Chagas' disease.

Left ventricular (LV) systolic dysfunction is a major prognostic determinant in Chagas' disease (ChD), a potentially fatal disorder which affects nearly 20 million individuals in Latin America. Therefore, reliable screening methods are needed to identify patients in need of a detailed evaluation of LV function. Since previous reports have suggested that a prolonged QRS duration may be an accurate predictor of LV dysfunction, the relationship between QRS duration and LV function was evaluated in ChD patients, in order to determine whether a narrow QRS on surface electrocardiogram (ECG) predicts a normal LV function. Ninety-eight patients with ChD and no other cardiac or systemic illness were underwent standard 12-lead ECG and Doppler echocardiogram (echo) examination. An investigator (blinded to the echo data) measured manually the QRS duration. LV dysfunction was defined by the presence of LV dilatation (LV diastolic dimension > 55 mm), depressed LV ejection fraction (LVEF < 0.50), segmental contractile abnormalities (SCA) or LV aneurysm. QRS duration was significantly correlated with LV diastolic dimension (r = 0.44, P = 0.000) and LVEF (r = 0.24, P = 0.016). A significant percentage of patients with QRS < 100 ms had abnormal systolic LV parameters, including LV dilatation (8.1%), reduced EF (10.2%), SCA (42.8%) and LV aneurysm (14.2%). A narrow QRS does not exclude the presence of significant global and segmental LV dysfunction in ChD patients. Since these abnormalities have prognostic and therapeutic implications, further evaluation of LV systolic performance is desirable in such patients.